#include <iostream>
	
#include <fstream>
	
using namespace std;
	
ifstream fin("fractii.in");
	
ofstream fout("fractii.out");
	
int x[1000000],n,i,j;
	
long long numere;
	
 
	
int main()
	
{
	
    fin>>n;
	
    for(i=2;i<=n;i++)
	
    x[i]=i-1;
	
    for(i=2;i<=n;i++)
	
    {numere+=x[i];
	
    for(j=i+i;j<=n;j+=i)x[j]-=x[i];
	
    }
	
    fout<<numere*2+1;
	
    return 0;
	
}